JPH0125730B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD This invention relates generally to the hydrogenation of aromatic ketones to alcohols, and specifically to improved methods for hydrogenating acetophenone to phenylmethyl carbinol (methylbenzyl alcohol). The reaction of hydrogenating acetophenone to phenylmethyl carbinol is of particular industrial interest since dehydration of phenylmethyl carbinol yields styrene (see US Pat. No. 3,526,674). Phenylmethyl carbinol can be obtained by the oxidation of ethylbenzene as proposed in the prior art or as a by-product when producing propylene oxide by the reaction of propylene with ethylbenzene hydroperoxide (U.S. Pat. 3551635 and 3350422). Catalysts for carrying out this hydrogenation have been known for some time. US Pat. No. 1,247,629 describes the use of catalytic metals with an atomic weight of 55 to 59, such as nickel, cobalt, iron, etc., for the hydrogenation of acetophenone. US Pat. No. 2,334,100 describes a process for the hydrogenation of alkylaryl ketones including acetophenone using a composite catalyst consisting of copper, zinc and alumina. The general application of copper chromite catalysts to the hydrogenation of carbon-bound unsaturated oxygens, including the conversion of ketones to alcohols, is described in US Pat. No. 2,137,407. Example 3 of the same specification includes a barium-modified copper chromite catalyst by precipitation of barium cuprammonium chromate produced by using ammonium dichromate and ammonium hydroxide in an aqueous solution of barium nitrate and copper nitrate. The manufacturing method is described. U.S. Patent No. 2125412
The patent describes the use of barium-containing and barium-free copper chromite catalysts for the hydrogenation of the keto groups of aromatic ketones having at least three benzene rings. A series of patents relating to the production of phenylmethyl carbinol by hydrogenation of acetophenone include U.S. Pat. No. 2,544,756, U.S. Pat. No. 2,554,771, U.S. Pat. These patent specifications relate in particular to improvements in copper-chromium based catalysts that have been successfully used for this type of hydrogenation. More recently, US Pat. Nos. 3,927,120 and 3,927,121 describe the use of metallic copper dispersed in a zinc oxide matrix as a catalyst for the production of phenylmethyl carbinol by hydrogenation of acetophenone. This patent describes preferred catalyst compositions and states that certain diluents have been found to improve conversion and selectivity in hydrogenation reactions. It should be noted that it is preferable to carry out the hydrogenation of acetophenone to the extent that it produces the corresponding alcohol, ie, phenylmethyl carbinol. Excess hydrogenation produces ethylbenzene, which is of lower value than phenylmethyl carbinol because it must be reoxidized to the appropriate alcohol to convert to styrene. Therefore, it is desirable to produce phenylmethyl carbinol using as little amount of ethylbenzene as possible, that is, to increase the production selectivity of phenylmethyl carbinol. It has been found that when copper pellets dispersed in a zinc oxide matrix are used for the hydrogenation of liquid acetophenone, they rapidly lose both their catalytic activity and their physical strength and must be replaced at an early stage. A catalyst is needed that not only has a high selectivity for the production of phenylmethyl carbinol but also has higher physical strength. Copper chromite, which is used in the hydrogenation of acetophenone, is also thought to have relatively poor strength when formed into pellets (for example, in U.S. Pat.
3256208 and 3235514), it is preferable for fixed bed hydrogenation if pellets with greater strength than copper chromite alone can be prepared. Two patent specifications of interest regarding the catalyst preparation method detailed herein are U.S. Pat.
No. 3256208 and Specification No. 3840478. These patent specifications relate to the preparation of catalysts particularly suitable for the production of methanol carried out by reacting carbon monoxide and hydrogen in the gas phase. These patent specifications describe the thermal decomposition product of cuprammonium chromate (copper chromite) as chromium trioxide and zinc (in Patent No. 3840478 as zinc carbonate, in Patent No. 3256208 as zinc oxide, (as zinc acetate or zinc hydroxide). Same No. 3840478
The catalysts described therein further contain copper in the form of basic copper carbonate. Hydrogenating acetophenone using an improved catalyst that has a high selectivity to the target product and has substantially higher physical strength after being subjected to a liquid phase reaction than the copper-zinc oxide catalyst used so far. An improved process for producing phenylmethyl carbinol has been provided by the present invention. The catalyst for the liquid phase hydrogenation of acetophenone to produce phenylmethylcarbinol consists essentially of a barium-containing zinc compound, typically zinc nitrate, and preferably magnesium chromate. Consists of copper chromate catalyst. Barium-containing copper chromite is prepared by coprecipitating barium, copper and chromium as cuprammonium chromate by adding ammonium dichromate and ammonium hydroxide from an aqueous solution of barium nitrate and copper nitrate. be able to. Other known methods of preparing copper chromite catalysts may alternatively be used. Barium-containing copper chromite powder is produced by drying the precipitated barium copper ammonium chromate at 250-400℃.
Preferably obtained by calcination at about 340-370°C in the presence of air. Calcined barium copper chromite powder can be impregnated with a solution of zinc compounds. Preferably, the calcined barium copper chromite powder is combined with a zinc compound and/or magnesium chromate in the form of a wet paste. Paste is 50
Dry at ~200℃, preferably 140-180℃ to remove almost all moisture, then dry in air for about 200℃
Calcined at ~400°C, preferably about 225-350°C.
The catalyst is prepared by grinding the calcined product into fine particles, preferably on a Tyler sieve to a particle size of about 20 to 30 mesh;
These granules are then prepared by pelletizing them with a small amount of graphite or other lubricant to the required size for use in a fixed bed reactor. Magnesium chromate can be dry blended with barium copper and zinc chromite compounds as a powder and then the dry blended powder can be formed into a wet paste, or alternatively magnesium chromate can be mixed with stoichiometric amounts of magnesium oxide and trioxide. React each aqueous solution containing chromium to produce magnesium chromate,
A zinc compound may then be added and the resulting solution added to the barium copper chromite. The prepared catalyst is (a) approximately 30 to 55 in terms of oxides;
wt% CuO, about 30-57 _wt % _Cr2O3 and about
barium copper chromite having a composition consisting of up to 16% by weight BaO; and (b) about 1 to 13% by weight ZnO based on 100% by weight of the barium copper chromite.
Contains. MgO is barium copper chromite 100
It can be contained in an amount of 0.15 to 1.7% by weight. Preferably the catalyst composition is about 40 to
Barium copper chromite with a composition consisting of 45% by weight CuO, about 40-47% by weight Cr ₂ O ₃ and about 8-12% by weight BaO, each based on 100% by weight of said barium copper chromite. Approximately 2.5-7.5% by weight ZnO
and about 0.5-1.2% by weight MgO. The catalyst of the present invention can be used at temperatures between 50 and 200°C and at gauge pressures.
In the process of the invention for producing phenylmethyl carbinol by liquid phase hydrogenation of acetophenone using a pressure of 20 to 140 Kg/cm ² and at least 1 mole of hydrogen per mole of acetophenone, the catalyst of the prior art It has superior selectivity and physical strength. The process of the invention is particularly intended for use in the production of phenylmethyl carbinol by liquid phase hydrogenation of acetophenone. This reaction is
It can be carried out by passing a liquid feed through a reactor in which hydrogen gas is dispersed and the reactants are brought into contact with a powdered catalyst. This type of process is called a slurry reaction because the catalyst forms a slurry in the reaction mixture. However, since slurry reactions are disadvantageous, it is desirable to use fixed bed catalysts. Catalysts used in fixed beds must be formed into pellets to provide passage for the reactants through the catalyst bed. As mentioned above, it has been known that prior art copper-zinc oxide catalysts have poor strength when used in a fixed bed, and a stronger catalyst with improved performance has been desired. Copper chromite is also known to have relatively low strength, and there has been a search for pellets with greater strength than pellets made from copper chromite alone. Broadly speaking, the catalyst of the present invention contains the metals copper, chromium, barium, zinc and magnesium, and essentially contains (a)30 in terms of their corresponding oxides.
~55 wt% CuO, 30-57 wt% _{Cr2O3 and}
barium copper chromite containing up to 16% by weight BaO; and (b) the barium copper chromite 100
It has a composition of 1 to 13% by weight of ZnO. Additionally, the composition may contain 0.15 to 1.7% MgO by weight based on 100% barium copper chromite. Preferably, the catalyst composition, expressed in terms of the corresponding oxide, contains (a) 40 to 45% by weight;
of CuO, 40-47% by weight of _Cr2O3 and 8-12% by weight of _BaO , and (b) 2.5-7.5% by weight of the barium copper chromite, respectively. wt% ZnO and 0.5-1.2
Contains % MgO by weight. The amount of barium used can vary considerably, as is clear from the wide range given above, but since barium is known to be a cocatalyst for copper chromite, some amount of barium may be present. preferable. Metals are
It is understood that it is more convenient and accurate to express compositional ranges as specific oxides than to describe the actual forms that these metals exhibit in the finished catalyst or in use. There will be. When prepared, the catalyst of the present invention contains barium copper chromite, which has been determined to be a composition whose chemical formula can vary depending on the amount of reactants. When zinc compounds and magnesium chromate are added to barium copper chromite and the mixture is calcined in air, the resulting catalyst is likely to contain each of these metals in oxidized form, although the exact composition is unknown. It has not been done. Therefore, in order to avoid ambiguity in presentation and for consistency, the compositions presented herein are based on the corresponding metal oxides. The first step in preparing the catalyst of the present invention is to make a barium-containing copper chromite catalyst powder by methods generally similar to those of the prior art. One way to prepare such copper chromite catalyst powder is to dissolve appropriate amounts of copper nitrate trihydrate and barium nitrate in distilled water, and to this add a solution of ammonium dichromate and ammonium hydroxide. The barium cuprammonium chromate is thus precipitated, the precipitate is filtered from the solution, washed with distilled water and dried, generally above 100°C, typically at about 110°C, to activate the barium cuprammonium chromate. calcination in air at 250 DEG to 400 DEG C., preferably about 340 DEG to 370 DEG C., for at least 2 hours to convert the copper chromite catalyst containing barium promoter. Alternatively, barium copper chromite powders can be prepared by other methods known in the art and described in the aforementioned literature, such as using carbonates from nitrates and other salts of copper, chromium and barium. It can be prepared by precipitation. The barium copper chromite catalyst powder is prepared and then optionally mixed with aqueous acetic acid, typically about 10
% acetic acid, washed with distilled water, approx.
The catalyst can also be activated by drying at temperatures above 100°C. It has been found that contact with acetic acid increases the catalytic activity of such chromite catalyst powders (see, for example, US Pat. No. 1,746,783). The barium promoter-containing copper chromite catalyst powder is prepared before the other ingredients are added to form the final catalyst, usually in the form of pellets. Although this catalyst can be used in the slurry reaction in powder form in some cases, pellets with high strength are particularly desirable. It will be appreciated that the zinc compound is added to improve the phenylmethyl carbinol production selectivity of the catalyst. This addition can also be made by impregnating pellets formed from barium copper chromite with the solution, but preferably the zinc compound is added in combination with the magnesium chromate. The particular form in which the zinc is added is not critical and can be any form that can decompose to the oxide form of zinc during calcination of the product catalyst. Typically, it is in the form of water-soluble zinc salts such as nitrates, acetates, hydroxides, carbonate-hydroxides, and the like. At least two methods have been found to produce sufficient catalyst pellets. The first method can also be called dry compounding, and the second method starts from an aqueous solution, but both methods form a wet paste that is then dried and calcined to form pellets. Make the final powder. In the first method, the barium copper chromite powder is dried and the MgO in the produced catalyst is about 0.15~
1.7% by weight of magnesium chromate MgCrC ₄ and zinc oxide in the resulting catalyst from about 1 to
Combine with zinc (typically in the form of zinc nitrate hexahydrate) to give 13% by weight. After dry blending, add enough water to make a wet paste and thicken (Kne(a)d) thoroughly to make a homogeneous mixture. Following the mixing process, the wet paste is mixed between 50 and 200
Drying at a temperature of 140-180°C, preferably for a time sufficient to remove almost all of the free water. This step usually takes up to about 3 hours to carry out, although typically 2 hours has been found to be sufficient in many cases. After the drying step, the catalyst is calcined in air at about 200-400°C, preferably about 225-350°C, for a time sufficient to convert the dried catalyst to the activated form. Typically, about 3 hours is sufficient. The catalyst of the present invention is granulated by passing through a 20-30 mesh Tyler sieve to obtain a uniform particle size for introduction into conventional pelletizing equipment. Generally about 2% graphite or other lubricant is added to the catalyst particles to facilitate pelletization. Catalyst pellets can be of any suitable size, but are typically about 4.76 mm in diameter.
(approximately 3/16″) and 3.175mm (1/8″) thick.
Preferably the pellet crushing strength is 15.9±2.27Kg
(35±5 pounds). Note that the use of higher compression forces provides higher crushing strength at the cost of lower effective surface area. A low crushing strength is undesirable since the pellets with low strength tend to fracture under the stress exerted by the reactant flow and the dead weight of the catalyst bed. Since it is important that the strength of the catalyst does not decrease even if it is exposed to reaction conditions for a long time, measurement of crushing strength is an important indicator of the performance of the catalyst. Crushing strength, as referred to herein, is tested by the method described below, and the results are expressed as the weight required to crush individual pellets. Each pellet was placed on a universal test stand model LTCM (by John John of Kew Gardens, New York).
(produced by Chatellon & Sons), the pellet is gradually moved in the diametrical direction against the spring-forced pointer.
Apply force to the testing machine at a constant speed. Once the pellets are destroyed, the power will be released. The pointer is locked to the maximum value and read as the crushing strength of the pellet being tested. Another catalyst preparation method does not add zinc chromate as a compound as was done in the previous method. Instead, chemically react magnesium oxide and chromium trioxide in stoichiometric proportions in water to form a solution containing the same amount of magnesium chromate as dry compounded in the first method. Depending on the situation, make adjustments first. Adding the required amount of zinc compound to the magnesium chromate solution and then mixing the mixed solution with barium copper chromite powder with distilled water if necessary to form a wet paste;
This is then mixed, dried and calcined as before. Catalyst pellets prepared in the manner described above have been found to provide improved results in the liquid phase hydrogenation of acetophenone to produce phenylmethyl carbinol. Typically, these reactions are carried out under conditions that favor the production of phenylmethyl carbinol and minimize the production of ethylbenzene. The temperature is 50-200℃, preferably 135-155℃, and the pressure is generally about gauge pressure.
20-140Kg/cm ² , preferably gauge pressure about 80Kg/cm ²
It is. There is no criticality to the amount of hydrogen used; at least 1 mole, preferably about 1 to 10 moles, of hydrogen is used per mole of acetophenone. In industrial operations, acetophenone is expected to be diluted to improve its activity and selectivity to the target product, phenylmethyl carbinol, as described in U.S. Pat. Nos. 3,927,120 and 3,927,121. will be done. For example, typical feedstocks contain about 20-60% by weight acetophenone in other hydrocarbons such as ethylbenzene, benzene, toluene, styrene, pseudocumene, and the like. It has been found that the addition of zinc to barium copper chromite significantly improves the selectivity of the hydrogenation of acetophenone and thus reduces the production of ethylbenzene. This effect is demonstrated in the following example. Example 1 A barium copper chromite catalyst is prepared as follows. That is, appropriate amounts of copper nitrate trihydrate and barium nitrate are dissolved in distilled water at 70°C, then an appropriate amount of ammonium dichromate solution dissolved in distilled water is added, and mixed with a 28% ammonium hydroxide solution. to precipitate barium cuprammonium chromate. The precipitate was filtered from the solution, washed with distilled water, dried at 110 °C, and calcined at 360 °C for 2 hours to obtain 45 wt% CuO,
Make barium copper chromite containing 45% _by weight _Cr2O3 and 10% by weight BaO. 2% catalyst powder
Molded using graphite with a crushing strength of approx.
The pellets weigh 13.6±2.27Kg (approximately 30±5 pounds). Part of the pellet was impregnated with an aqueous solution of zinc nitrate hexahydrate, dried at 110℃ for 2 hours, and then dried at 250℃ for 3 hours.
Calcinate in air for an hour. Zinc-impregnated catalyst pellets are approximately 3.4% by weight based on barium copper chromite.
of ZnO. Zinc-impregnated pellets and zinc-free pellets were placed in a batch reactor, respectively, and heated with acetophenone (ACP) and hydrogen at 135°C and gauge pressure.
Contact was made at 84Kg/ ^cm2 . Under standard conditions, 4/hour hydrogen gas per 1g of catalyst, 46.5% acetophenone
When passed through 34 g of liquid feed containing 44.8 wt% pseudocumene, 8.4 wt% phenylmethyl carbinol and 0.3 wt% ethylbenzene (EB) for 4 hours, acetophenone was almost completely converted to phenylmethyl carbinol. Ta. Table 1 shows the results of the two types of catalysts.

[Table] It can be seen that although the activity of the catalyst decreases with the addition of zinc, the selectivity is improved by a factor of 4. This is a very important advantage in the industrial hydrogenation of acetophenone. Example 2 About 45% by weight of CuO by the method of Example 1,
A barium copper chromite catalyst powder is made containing about 45% _by weight _Cr2O3 and about 10% by weight BaO. 3.1% by weight of magnesium chromate powder and 24.4% by weight of zinc nitrate hexahydrate powder are blended into the base powder in a dry state. Add enough water to make a wet paste, thicken thoroughly, dry in air at 170°C for 2 hours, then calcinate in air at about 250°C for 3 hours.
The calcined catalyst was pulverized through a 20-30 mesh sieve and pelletized with 2% graphite to form a pellet with a diameter of 4.76 mm (3/16") and a thickness of 3.175 mm (1/2").
8″), initial crushing strength 15.9±2.27Kg (35±5 lbs)
pellets. The catalyst pellets are placed in a batch reactor and contacted with acetophenone and hydrogen at 135° C. and 84 kg/cm ² gauge pressure. 4 in standard conditions for 1g of catalyst
/ hour of hydrogen gas, 46.5% by weight of acetophenone, 44.8% by weight of pseudocumene, 8.4% by weight of phenylmethyl carbinol and 0.3% by weight of ethylbenzene.
The acetophenone was almost completely converted to phenylmethyl carbinol when passed through 34 g of liquid feed containing % by weight for 4 hours. The calculated results of the catalyst (B) prepared as described above are shown in Table 1. Table 1 lists the activity and selectivity of catalyst (B) for prior art catalyst (A) (C-61-1 obtained from Catalyst and Chemicals Inc.) and Example 1 using the same reaction conditions. compared with those of catalyst (C) prepared by

[Table] From the table, the activities of catalysts (B) and (C) are slightly lower than the activity of catalyst (A) of the prior art, but catalyst (B)
The selectivity towards phenylmethyl carbinol is very good as shown by the relatively low amount of ethylbenzene produced by (C) and therefore the prior art catalyst (A). It can be seen that this is a substantial improvement. While this short batch experiment shows that the activity of catalysts (B) and (C) is comparable to prior art catalysts, experiments conducted in a continuous flow reactor show that catalyst (B) and (C) B) and
It was found that (C) maintained a higher activity for a longer period of time than the copper-zinc oxide catalyst (A). Therefore, it can be expected that the catalyst of the present invention exhibits superior average activity and can be used continuously for a substantially longer period of time than the catalysts of the prior art. Example 3 About 41% by weight of CuO by the method of Example 2,
_Cr2O3 approx. 41.5% by weight, BaO approx. 8% by weight, _ZnO approx. 6.2
A catalyst (B) having a composition of about 0.83% by weight and MgO is prepared. The catalyst was placed in a basket fixed in an autoclave (continuously stirred tank reactor) and subjected to continuous flow conditions at approximately 155° C. and a gauge pressure of 84 Kg/cm ² . The overall space velocity of the liquid is
10WHSV, and approximately 7.6 mol of hydrogen is supplied per 1 mol of acetophenone supplied. Liquid raw materials are approximately 37.8% by weight of acetophenone and approximately 49.2% by weight.
of ethylbenzene, about 6.9% by weight phenylmethyl carbinol and about 2.9% by weight styrene. After 100 hours of operation, the catalyst was removed from the reactor and its crushing strength was compared to that of the prior art catalyst (A) subjected to substantially identical processing conditions.
C-61-1) obtained from Chemicals Inc. and the catalyst (C) of Example 1. The measured values are shown in the table below.

[Table] It can be seen from the table that even after a relatively short period of 100 hours of operation, the prior art catalyst loses approximately two-thirds of its freshly prepared crushing strength. In contrast, catalyst (B) shows only a slight decrease of less than 10% after 100 hours of use, and catalyst (C) shows a decrease but still a high value. These results demonstrate a significant improvement in the strength of the catalyst of the present invention over prior art catalysts. The foregoing discussion of the method of the present invention is for illustrative purposes and should not be considered as limiting the scope of the claimed invention.

Claims (1)

[Claims] 1 Expressed as oxide (a) 30-55% by weight of CuO, 30
barium copper chromite containing ~57% by weight _Cr2O3 and up to 16% by weight BaO, and (b) 1 _to 13 based on the weight of said barium copper chromite.
wt% ZnO, or 1 to 13 wt% ZnO and
Acetophenone and hydrogen were heated at a temperature of 50 to 200 °C and a pressure of 20 to 140 °C over a fixed bed of catalyst pellets having a composition of 0.15 to 1.7% by weight of MgO.
A method for producing phenylmethyl carbinol by hydrogenating acetophenone, the method comprising contacting 1 mole of acetophenone with at least 1 mole of hydrogen under a pressure of Kg/cm ² .